Access Container View Controller from Parent iOS

Question

in iOS6 I noticed the new Container View but am not quite sure how to access it\'s controller from the containing view.

Scenario:

Answer 1

I use Code like:

- (IBAction)showCartItems:(id)sender{ 
  ListOfCartItemsViewController *listOfItemsVC=[self.storyboard instantiateViewControllerWithIdentifier:@"ListOfCartItemsViewController"];
  [self addChildViewController:listOfItemsVC];
 }

Answer 2

you can write like this

- (IBAction)showDetail:(UIButton *)sender {  
            DetailViewController *detailVc = [self.childViewControllers firstObject];  
        detailVc.lable.text = sender.titleLabel.text;  
    }  
}

Answer 3

You can do that simply with self.childViewControllers.lastObject (assuming you only have one child, otherwise use objectAtIndex:).

Answer 4

The prepareForSegue approach works, but it relies on the segue identifier magic string. Maybe there's a better way.

If you know the class of the VC you're after, you can do this very neatly with a computed property:

var camperVan: CamperVanViewController? {
  return childViewControllers.flatMap({ $0 as? CamperVanViewController }).first
  // This works because `flatMap` removes nils
}

This relies on childViewControllers. While I agree it could be fragile to rely on the first one, naming the class you seek makes this seem quite solid.

Answer 5

An updated answer for Swift 3, using a computed property:

var jobSummaryViewController: JobSummaryViewController {
    get {
        let ctrl = childViewControllers.first(where: { $0 is JobSummaryViewController })
        return ctrl as! JobSummaryViewController
    }
}

This only iterates the list of children until it reaches the first match.